Recently, relationship between enteric bacteria and carcinogenesis has been researched progressively. Particularly, it is said that change in intestinal bacterial flora plays a major role in the formation of carcinogens and substances for promoting carcinogenesis and their activation or suppression.
Especially, utility of lactic acid bacteria attracts attention and it is said that immune response of a host may be improved by supplying lactic acid bacteria or products of cultivation thereof, and that lactic acid bacteria may suppress proliferation of intestinal bacteria relating to production of carcinogens and carcinogenesis-promoting substances to suppress occurrence of tumors.
However, which substance among products of lactic acid bacteria provides such effects has not known yet.
Besides, Lactic acid is well known as a main substance produced by lactic acid bacteria. Lactic acid is an usual component in animal's bodies and is produced in muscles. Most of produced lactic acid is utilized as a substrate for TCA cycle or gluconeogenesis in the liver or kidney.